Compostition and therapeutic anti-tumour vaccine

ABSTRACT

The invention relates to a composition which induces, in a host, a cytotoxic cell response directed against cells expressing an antigen, in particular tumour cells, and which comprises red blood cells containing said antigen. These red blood cells may be in the form of an immune complex with an immunoglobulin, in particular IgG, which recognizes an epitope at the surface of the red blood cells, and/or be heat-treated or chemically treated so as to promote phagocytosis of said red blood cells by dendritic cells. As a variant, the red blood cells may be xenogenic red blood cells. The invention also relates to a therapeutic especially anti-tumour vaccine containing such a composition.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. provisional patent application60/954,917, filed Aug. 9, 2007, and French patent application, FR 0705767, filed Aug. 8, 2007, both herein incorporated by reference.

The present invention relates to a composition which induces, in a host,a cytotoxic response for anti-tumour purposes, and also to a therapeuticanti-tumour vaccine containing this composition.

The natural immune response against tumour antigens is relativelyineffective and various mechanisms allowing tumours to escape theanti-tumour immune response have been identified. Conventional vaccineapproaches generate humoral responses which prove to be insufficient.

Strategies aimed at developing a cytotoxic response based onantigen-presenting cells (APCs), in particular based on dendritic cells,have been studied. The principle consists in specifically destroying thecancer cells of a patient by stimulating said patient's own immunedefenses.

Dendritic cells are antigen-presenting cells (APCs) that are veryeffective in generating cytotoxic effectors specific for tumour cells.They are capable of phagocytizing apoptotic cells or apoptotic bodiesoriginating from tumour cells, and then of presenting the tumourantigens, in association with MHC class I and II molecules, to Tlymphocytes. Thus, the dendritic cell is capable of initiating theproliferation and the generation of a clone of specific cytolytic Tlymphocytes. At the end of this reaction, the killer lymphocytes thusdifferentiated leave the lymphoid compartment so as to circulate in theorganism and bind in the tumour. Recognition of the antigens expressedby a tumour then induces a lytic signal and brings about the destructionof the tumour cells.

Several anti-cancer vaccine strategies targeting dendritic cells havebeen studied (Eymard J C, Bernard J, Bull Cancer. 2003, 90(8-9):734-43).Some are based on manipulating the dendritic cells in vitro, and othersare based on stimulating the dendritic cells in vivo. In the first case,the dendritic cells are differentiated from blood cells taken from thepatient: they are cultured and matured, “pulsed”, i.e. stimulated, exvivo with tumour peptides, tumour lysates, apoptotic tumour cells, orheat shock proteins extracted from autologous tumours, and finallyreinjected into the patient. In the second case, the stimulation of thedendritic cells is carried out after injection, into the patient, ofpeptides, proteins, irradiated tumour cells or else viruses containingthe antigenic peptide targeting the dendritic cells. However, thecytotoxic response obtained is rarely accompanied by clinical efficacy.The activation of the dendritic cell “conditions” its ability toeffectively activate the cytolytic T lymphocyte. The level of activationof dendritic cells appears to be a delicate point in this vaccinestrategy.

The use of dendritic cells ex vivo for obtaining an anti-tumour vaccineraises a certain number of issues on: the state of maturation of thedendritic cells, the number of cells to be injected, the route, the siteand the frequency of injection for producing dendritic cells capable ofmigrating to the secondary lymphoid organs and of inducing an effectivecytotoxic T response (Banchereau J, Schuler-Thurner B, Palucka A K,Schuler G. [Dendritic cells as vectors for therapy] Cell. 2001, 10,106(3): 271-4.).

The activation of dendritic cells in vivo is, for its part, limited bythe weak immunogenic capacity of tumour antigens and the difficulty inactivating dendritic cells at a sufficient level.

The use of red blood cells as carriers for transporting antigens,encapsulated in the red blood cells or bound to their surface, anddelivered to the APCs has been envisaged in several publications. Thetriggered immune responses have been investigated in vitro and in vivo.

Hamidi et al. have recently described the encapsulation of BSA (bovineserum albumin) as a model of an antigen in human red blood cells (HamidiM et al., Drug Deliv., 2007; 14(5):295-300 and Int J Pharm., 2007, 29,338(1-2): 70-8). The authors suggested the use of red blood cells as avector for the presentation of antigens to APCs of thereticuloendothelial system (RES). In another review published by Hamidiet al. (J. Control. Release, 2007, 118(2): 145-60), the authorsindicated that a certain number of strategies have been studied topromote targeting of the RES, said targeting being promoted by ageing ofthe red blood cells, leading to their uptake for lysis. Other routeswere mentioned, such as exposure of red blood cells to stabilizingagents, in particular crosslinking agents, coating of red blood cellswith anti-RH antibodies, of IgG type to target the spleen or of IgM typeto target the liver, heat shock, or exposure to oxidizing agents,enzymes or antibiotics.

A humoral immune response can be obtained in vivo after immunizationwith antigen-loaded red blood cells. The study carried out by Murray etal. made it possible to detect, in mice, IgG immunoglobulins afterintravenous injection of murine red blood cells loaded with one of thefollowing four antigens: KLH (Keyhole Limpet Haemocyanin), BSA (BovineSerum Albumin), CTB (Cholera Toxin b Subunit) and ADA (Bovine AdenosineDeaminase). Detection of IgG1 and IgG3, which are predominantimmunoglobulin isotypes during a Th2 response, and of IgG2,immunoglobulin isotype which is a marker for a Th1 response, wouldsuggest the involvement of both types of immune responses, the humoralresponse and the cellular response (Murray A M et al., Vaccine., 200628, 24(35-36): 6129-39).

Another formulation of antigens used with red blood cells has beentested by Dominici et al. The Tat protein of the HIV-1 virus wasanchored to the surface of mouse red blood cells by means ofavidin/biotin coupling. The immunization of mice by intraperitonealinjection with this antigen formulation, internalized by dendriticcells, triggered a humorally-mediated immune response in vivo. Isotypecharacterization of the immunoglobulins detected indicates the inductionof Th1 and Th2 responses. The anti-Tat cytotoxic activity was shown invitro, by the conventional chromium-release technique, for the micetreated with red blood cells coupled to the antigens (Dominici S et al.,Vaccine., 2003 16, 21(17-18): 2073-81).

A cellular response has been demonstrated in vitro by Corinti et al.with the same formulation. Phagocytosis of the red blood cellsconjugated with Tat protein, by dendritic cells derived from humanmonocytes, was shown, as was the induction of CD4+ and CD8+ responses.Moreover, maturation of dendritic cells in the presence of interferongamma promoted the type I immune response (Corinti S. et al., Leukoc.Biol. 2002, 71(4): 652-8).

Boberg et al. injected mice intraperitoneally with a vaccine constitutedof peptides derived from the HIV-1 protease anchored at the surface ofmouse red blood cells by means of the avidin/biotin system. Theychemically modified red blood cells with the aim of promoting theirrecognition by APCs, but a weak immune reaction was obtained. Theyconcluded that the small amount of antigens delivered, due to thelimited loading of red blood cells with antigenic peptides and bloodvolume injected was not compensated for by the chemical modification ofthe carriers supposed to promote antigen recognition by APCs (Boberg A.et al., Infect. Agents Cancer., 2007, 182: 9).

The present invention aims to provide compositions and vaccines that canbe used in the treatment of cancers, according to an immunotherapyapproach.

An object of the invention is therefore a composition which induces, ina host, a cytotoxic cellular response directed against tumour cells, andwhich comprises red blood cells containing a tumour antigen.

The term “host” refers preferably to humans, but also to animals, inparticular pets (especially dogs or cats) and animals for sport(especially horses).

According to the invention, the red blood cells contain, i.e.encapsulate, the antigen, which means that the antigen is or isessentially inside the red blood cell.

Said red blood cells are preferably designed, selected or modified so asto promote phagocytosis thereof by APCs, and most particularly bydendritic cells. In particular, said red blood cells are designed,selected or modified so as to promote phagocytosis thereof in the spleenand the liver, the essential objective being to target APCs of thespleen.

In a preferred embodiment, the compositions according to the inventioncomprise red blood cells which contain the antigen and target thespleen. The composition promotes phagocytosis of these red blood cellsby the APCs, in particular the dendritic cells, in the spleen.

According to a first embodiment, the red blood cells contain a tumourantigen and are in the form of an immune complex with an immunoglobulinwhich recognizes an epitope at the surface of said red blood cells, soas to promote the phagocytosis of said red blood cells, in particular bydendritic cells. The composition also makes it possible to promotephagocytosis by macrophages. Preferably, the immunoglobulin is animmunoglobulin G.

The formation of the immune complex involves red blood cells and atleast one antibody, preferably of IgG subtype. Dendritic cells have, attheir surface, receptors for the constant Fc region of immunoglobulins G(IgGs). These receptors are capable of triggering phagocytosis orinternalization of the antigen-IgG immune complexes thus formed and ofpromoting antigen presentation by MHC class I and II molecules,resulting in the generation of CD4⁺ helper lymphocytes and especiallyCD8⁺ cytotoxic lymphocytes (A. Regnault et al., J. Exp. Med., Janvier1999, 189(2): 371-80).

As antibodies which are suitable, mention may be made of anti-rhesusantibodies, anti-glycophorin A antibodies and anti-CR1 antibodies(CR1=complement receptor type 1). Anti-glycophorin A antibodies (A.Bigbee et al., Mol. Immunol., December 1983, 20(12): 1353-62) are apreferred modality.

Preferably, the red blood cells of human origin that are used to form animmune complex are heterologous red blood cells originating from adonor.

According to a second embodiment, the red blood cells contain a tumourantigen and are heat or chemically modified, so as to promotephagocytosis of said red blood cells, in particular by dendritic cells.The composition also makes it possible to promote phagocytosis bymacrophages.

The heat treatment is in particular carried out under the followingconditions: heating of red blood cells for about 15 minutes to about 90minutes, preferably from about 25 to about 50 minutes, at a temperatureof between about 42 and about 55° C., preferably between about 47 andabout 51° C. Typically, red blood cells are heated for about 30 minutesat between about 48 and about 50° C., for example at about 48° C.

The chemical treatment is carried out using agents which modify thesurface of red blood cells, and in particular bridging or crosslinkingagents such as bis(sulphosuccinimidyl)suberate (BS3 or BS³),glutaraldehyde or neuraminidase.

In a particular embodiment, at least two methods of targeting arecombined, and, for example, the composition then comprisesantigen-containing red blood cells which are in the form of an immunecomplex and are heat or chemically treated so as to promote their uptakein the spleen and/or the liver, preferably the spleen, and phagocytosisby APCs, in particular by dendritic cells.

In a third embodiment, the antigen-containing red blood cells arexenogenic. Injection of xenogenic red blood cells into humans results inthe binding of the patient's natural antibodies to the injected redblood cells. The immune complex thus formed promotes phagocytosis byAPCs, in particular by dendritic cells. Preferably, said red blood cellsare of porcine origin.

In a particular embodiment, the xenogenic red blood cells are heat orchemically modified so as to promote phagocytosis thereof.

The composition according to the invention may comprise one or moretumour antigens. When there are several tumour antigens, said tumourantigens are preferably selected so as to induce an immune responseagainst one type of tumour or of tumour cells.

The composition preferably comprises at least two tumour antigensrepresentative of the tumour to be treated. The objective is to generateseveral clones of cytotoxic T lymphocytes which each recognizes aspecific antigenic peptide so as to develop a more effective immuneresponse.

In a particular embodiment, the composition comprises at least twopopulations of red blood cells, each encapsulating a different antigen.

The most well known antigens that can be used herein are indicated inthe tables below, where they are classified by category.

Unique Antigens:

Gene/protein Tumour alpha-actinin-4 Lung carcinoma ARTC1 MelanomaBCR-ABL fusion protein (b3a2) Chronic myeloid leukaemia B-RAF MelanomaCASP-5 Colorectal, gastric and endometrial carcinoma CASP-8 Head andneck squamous cell carcinoma beta-catenin Melanoma Cdc27 Melanoma CDK4Melanoma CDKN2A Melanoma COA-1 Colorectal carcinoma dek-can fusionprotein Myeloid leukaemia EFTUD2 Melanoma Elongation factor 2 Squamouscell carcinoma of the lung ETV6-AML1 fusion protein Acute lymphoblasticleukaemia FN1 Melanoma GPNMB Melanoma LDLR-fucosyltransferaseAS fusionMelanoma protein HLA-A2d Renal cell carcinoma HLA-A11d Melanoma hsp70-2Renal cell carcinoma KIAAO205 Bladder tumour MART2 Melanoma ME1 “Nonsmall cell” lung carcinoma MUM-1f Melanoma MUM-2 Melanoma MUM-3 Melanomaneo-PAP Melanoma Myosin class I Melanoma NFYC Squamous cell carcinoma ofthe lung OGT Colorectal carcinoma OS-9 Melanoma pml-RARalpha-fusionprotein Promyelocytic leukaemia PRDX5 Melanoma PTPRK Melanoma K-rasPancreatic adenocarcinoma N-ras Melanoma RBAF600 Melanoma SIRT2 MelanomaSNRPD1 Melanoma SYT-SSX1 or -SSX2 fusion Sarcoma protein TriosephosphateIsomerase Melanoma FLT3-ITD Acute myeloid leukaemia p53 Head and necksquamous carcinoma

Antigens Common to Several Tumours:

a) Tumour-Specific Antigens

Genes BAGE-1 GAGE-1, 2, 8 GAGE-3, 4, 5, 6, 7 GnTVf HERV-K-MEL KK-LC-1KM-HN-1 LAGE-1 MAGE-A1 MAGE-A2 MAGE-A3 MAGE-A4 MAGE-A6 MAGE-A9 MAGE-A10MAGE-A12 MAGE-C2 mucin k NA-88 NY-ESO-1/LAGE-2 SAGE Sp17 SSX-2 SSX-4TRAG-3 TRP2-INT2g

b) Differentiation Antigens

Gene/protein Tumour CEA Intestinal carcinoma gp100/Pmel17 MelanomaKallikrein 4 Prostate mammaglobin-A Breast cancer Melan-A/MART-1Melanoma NY-BR-1 Breast cancer OA1 Melanoma PSA Prostate carcinomaRAB38/NY-MEL-1 Melanoma TRP-1/gp75 Melanoma TRP-2 Melanoma tyrosinaseMelanoma

c) Overexpressed Antigens

Gene Tissue expression adipophilin adipocytes, macrophages AIM-2Ubiquitous (low level) BING-4 Ubiquitous (low level) CPSF Ubiquitous(low level) cyclin D1 Ubiquitous (low level) Ep-CAM Epithelial cellsEphA3 Numerous FGF5 Brain, kidneys G250/MN/CAIX Stomach, liver, pancreasHER-2/neu Ubiquitous (low level) IL13Ralpha2 Intestinal carboxyl liver,intestine, kidneys esterase alpha-foetoprotein Liver M-CSF liver,kidneys mdm-2 ubiquitous (brain, muscle, lungs) MMP-2 Ubiquitous MUC1Glandular epithelium p53 Ubiquitous (low level) PBF ovaries, pancreas,spleen, liver PRAME Testes, ovaries, endometrium, adrenal glands PSMAprostate, CNS, liver RAGE-1 Retina RNF43 RU2AS testes, kidneys, bladdersecernin 1 Ubiquitous SOX10 Ubiquitous (low level) STEAP1 Prostatesurvivin Ubiquitous Telomerase testes, thymus, bone marrow, lymph nodesWT1 testes, ovaries, bone marrow, spleen BCLX (L) Ubiquitous (low level)DKK1 Testes, prostate, mesenchymatous stem cells ENAH (hMena) Breast,prostate, colon-rectum stroma and epithelium, pancreas, endometrium MCSPEndothelial cells, chondrocytes, nonstriated muscle cells RGS5 Heart,skeletal muscle, pericytes

Van der Bruggen et al. have produced a database referencing all humantumour antigens recognized by T lymphocytes and usable in cancerimmunotherapy approaches according to the invention:http://www.cancerimmunity.org/peptidedatabase/Tcellepitopes.htm.

Other antigens may be used in the invention such as: Gastrin 17, HumanChorionic Gonadotropin, EGFRvIII, HER2, HER2/neu, P501, Guanylyl CyclaseC, PAP.

The word antigen encompasses antigens of natural or synthetic orartificial origin, antigens originating from the patient to be treated,antigenic fragments, derivatives or variants, so long as the antigen isable to initiate the appropriate immune response. The antigens may befor example extracted, chemically synthesized or produced via geneticengineering.

In order to generate an effective immune response, dendritic cells haveto be active and mature, they have to produce cytokines and chemokinesand to express costimulation molecules that are necessary for therecruitment and activation of T lymphocytes.

Various types of adjuvants can be used to stimulate APCs, and inparticular dendritic cells. Bacterial or viral RNA or DNA, heat shockproteins (HSPS), sugars, immune complexes and cytokines are variousfactors which induce APC maturation, and in particular dendritic cellmaturation mediated by the stimulation of specific receptors (Toll-likereceptor TLR, mannose receptor). Macrophages and dendritic cells do notall express the same receptors at their surface. The choice of theadjuvant therefore relates to a molecule capable of generating acytotoxic immune response in humans and for which the receptor is foundat the surface of the cells taking up the red blood cells of theinvention, and therefore in particular at the surface of dendriticcells.

According to one embodiment, the adjuvant is a molecule encapsulatedinside red blood cells or attached to the surface of red blood cells.These are preferably the red blood cells containing the antigen.

Alternatively, the adjuvant is encapsulated in, or attached to thesurface of, other red blood cells treated separately. These red bloodcells may also be modified or selected so as to promote phagocytosisthereof by APCs, in particular by dendritic cells. They may thus be, aspreviously described, in the form of an immune complex, or thermally orchemically modified, or else be xenogenic.

According to another embodiment, the adjuvant is a separate adjuvantcomposition, that can be administered simultaneously with or separatelyfrom the red blood cells containing the antigen.

It goes without saying that, as long as the adjuvant can be in aseparate composition (red blood cell composition or adjuvantcomposition), the adjuvant can be administered concomitantly with thered blood cells containing the antigen, as a separate administration orin the form of a mixture, or administered separately, for example afterthe administration of the red blood cells comprising the antigen, inparticular a few hours or days apart.

Among the adjuvants that can be used, mention may first and foremost bemade of the preferred adjuvants below

-   -   TLRs (Toll-like receptors) ligands, in particular        imidazoquinolones, such as preferably: imidazoquinoline, e.g.        imidazoquinoline CL097, imiquimod, resiquimod; CpG        oligodeoxynucleotides; LPSs (lipopolysaccharides); poly(inosinic        acid)-(polycytidylic acid poly(I:C));    -   cytokines, in particular: interferon alpha, IL-2 (interleukin        2), IFNγ (interferon gamma), GM-CSF (Granulocyte Monocyte-Colony        Stimulating Factor), IL-12 (interleukin 12), TNFα (Tumour        Necrosis Factor alpha).

Among the other adjuvants that can be used, mention may in particular bemade of:

-   -   bacterial constituents, in particular BCG (Bacillus Calmette        Guerin), MDP (Muramyl dipeptide), TDM (Trehalose dimycolate),        LPS (lipopolysaccharide), MPL (monophosphoryl lipid A);    -   mineral adjuvants, in particular: aluminium hydroxide, aluminium        phosphate, potassium phosphate and calcium phosphate;    -   bacterial toxins, in particular: CT (cholera toxin from Vibrio        cholera), CTB (cholera toxin from Vibrio cholera), PT (pertussis        toxin from Bordetella pertussis) LT (thermolabile lymphotoxin        from Escherichia coli);    -   KLH, Keyhole limpet haemocyanin.

Techniques for encapsulating active ingredients in red blood cells areknown and the basic technique by lysis-resealing, which is preferredherein, is described in patents EP-A-101 341 and EP-A-679 101, to whichthose skilled in the art may refer. According to this technique, theprimary compartment of a dialysis element (for example, dialysis tubingor a dialysis cartridge) is continuously fed with a suspension of redblood cells, while the secondary compartment contains an aqueoussolution which is hypotonic with respect to the suspension of red bloodcells, in order to lyse the red blood cells; next, in a resealing unit,the resealing of the red blood cells is induced in the presence of thetumour antigen by increasing the osmotic and/or oncotic pressure, andthen a suspension of red blood cells containing the tumour antigen iscollected.

Among the variants described up until now, preference is given to themethod described in French Patent Application No. 0408667, which makesit possible to efficiently, reproducibly, safely and stably encapsulatethe tumour antigen. This method comprises the following steps:

1—suspension of a red blood cell pellet in an isotonic solution at ahaematocrit level greater than or equal to 65%, cooling between +1 and+8° C.,

2—measurement of the osmotic fragility using a sample of red blood cellsfrom said red blood cell pellet,

it being possible for steps 1 and 2 to be carried out in any order(including in parallel),

3—lysis and internalization process of the tumour antigen, inside thesame chamber, at a temperature constantly maintained between +1 and +8°C., comprising passing the suspension of red blood cells at ahaematocrit level greater than or equal to 65%, and a hypotonic lysissolution cooled to between +1 and 8° C., through a dialysis cartridge;and the lysis parameters being adjusted according to the osmoticfragility previously measured; and

4—resealing process carried out in a second chamber, inside which thetemperature is between +30 and +40° C., and in the presence of ahypertonic solution.

The “internalization” is intended to mean penetration of the tumourantigen inside the red blood cells.

In particular, for the dialysis, the red blood cell pellet is suspendedin an isotonic solution at a high haematocrit level, greater than orequal to 65%, and preferably greater than or equal to 70%, and thissuspension is cooled to between +1 and +8° C., preferably between +2 and6° C., typically in the region of +4° C. According to a specificembodiment, the haematocrit level is between 65% and 80%, preferablybetween 70% and 80%.

The osmotic fragility is advantageously measured on the red blood cellsjust before the lysis step. The red blood cells or the suspensioncontaining them are (is) advantageously at a temperature close to oridentical to the temperature selected for the lysis. According toanother advantageous feature of the invention, the osmotic fragilitymeasurement is exploited rapidly, i.e. the lysis process is carried outshortly after the sample has been taken. Preferably, this period of timebetween taking the sample and beginning the lysis is less than or equalto 30 minutes, more preferably still less than or equal to 25, and evenless than or equal to 20 minutes.

As regards the manner in which the lysis-resealing process is carriedout, with the osmotic fragility being measured and taken into account,those skilled in the art may refer to French Patent Application No.0408667 for further details.

According to one feature of the invention, the composition according tothe invention comprises, at the end, a suspension of red blood cells ata haematocrit level of between about 40% and about 70%, preferablybetween about 45% and about 55%, better still about 50%. It ispreferably packaged in a volume of about 10 to about 250 ml. Thepackaging is preferably in a blood bag of the type suitable for bloodtransfusion. The amount of encapsulated tumour antigen corresponding tothe medical prescription is preferably entirely contained in the bloodbag.

An object of the present invention is also a therapeutic anti-tumourvaccine comprising an effective amount of one or more compositionsaccording to the invention. Thus, the vaccine may comprise a compositionaccording to the invention, itself containing a population of red bloodcells encapsulating one or more tumour antigens, in the presence orabsence of encapsulated or nonencapsulated adjuvant, or at least twocompositions according to the invention with different populations ofred blood cells encapsulating one or more tumour antigens, in thepresence of encapsulated or nonencapsulated adjuvant.

An object of the invention is also a method for inducing, in a patient,a cytotoxic cellular response against tumour cells or a tumour. Thismethod comprises the administration to this patient of an effectiveamount of a composition according to the invention, in particularintravenously, by injection or infusion, preferably by infusion. Thismethod is aimed in particular at inducing activation of the patient'sdendritic cells and a CD8⁺ cytotoxic cellular response. As describedabove, a specific CD4⁺ helper and CD8⁺ cytotoxic response is obtained.

An object of the invention is also an anticancer treatment method forinducing, in a patient, a cytotoxic cellular response as describedabove, against tumour cells or a tumour. This method comprises theadministration to this patient of an effective amount of an anti-tumourvaccine according to the invention, in particular intravenously, byinjection or infusion, preferably by infusion.

According to one feature of the invention, about 10 to about 250 ml of asuspension of red blood cells at a haematocrit level of between about40% and about 70%, preferably between about 45% and about 55%, betterstill about 50%, are administered.

An object of the invention is also the use of a composition according tothe invention, for the manufacture of a therapeutic anti-tumour,vaccine.

An object of the invention is also the use of a composition according tothe invention, for inducing, in a host, a cytotoxic cellular responsemediated by dendritic cells and directed against tumour cells or atumour.

Another object of the invention is a composition according to theinvention, for use as a therapeutic anti-tumour vaccine.

The present invention will now be described in greater detail by meansof embodiments taken by way of nonlimiting examples, and which refer tothe attached drawings.

FIG. 1: Measurement of the phagocytosis of “antigen-loaded” red bloodcells treated with the anti-TER 119 antibody, by spleen dendritic cellsin vitro.

FIG. 2: Measurement of the phagocytosis of “antigen-loaded” red bloodcells treated with the anti-TER 119 antibody or heat-treated, by spleenmacrophages and dendritic cells in vivo.

FIG. 3: Graph illustrating the proliferation and activation ofovalbumin-specific CD4 T cells 3 days after injection into mice.

(A) Cell division induces a reduction in the intensity of CFSEfluorescence. OVA-specific CD4 T cells lose half of their fluorescentmaterial on each division. The peak observed for batch 4 representsundivided cells having a large CFSE content. All of the other peaksrepresent cells which have undergone 1, 2, 3, 4, 5, 6 or 7 celldivisions. When the cells have divided more than 8 times, the CFSEcontent of the cells is practically zero.

(B) CD44 cell activation marker expression is represented as a functionof the number of divisions occurring.

EXAMPLE 1 Method for Encapsulating Ovalbumin in Murine and Human RedBlood Cells and in Porcine Red Blood Cells Variant 1

Ovalbumin (protein of 45 kDa, hen egg ovalbumin) is encapsulated inmurine red blood cells (OF1 mice or C57Bl/6 mice) by the method ofhypotonic dialysis in dialysis tubing. The red blood cell suspension iswashed several times before being brought to a haematocrit of 70% forthe dialysis. The dialysis is carried out in dialysis tubing in a lysisbuffer of low osmolarity for about 1 hour or 30 min when the dialysisoccurs after a heat treatment. The red blood cells are then resealed bymeans of a solution of high osmolarity for 30 minutes. After a fewwashes, the final product is taken up in a buffer, Sag-mannitol, andhaematocrit is brought to 50%.

Variant 2 for Example 1

Ovalbumin is herein encapsulated in the murine red blood cells by themethod of hypotonic dialysis in a dialysis column. The red blood cellsuspension is washed several times before being brought to a haematocritof 70% for the dialysis. The dialysis is carried out in a dialysiscolumn in a lysis buffer of low osmolarity for about 10 min. As soon asthey leave the column, the red blood cells are resealed by means of asolution of high osmolarity for 30 minutes at 37° C. After a few washes,the final product is taken up in a NaCl glucose buffer containingglucose SAG mannitol, or decomplemented plasma, and haematocrit isbrought back to 50%.

EXAMPLE 2 Heat Treatment on the Red Blood Cells

When the encapsulation is realized according to variant 1 of example 1,heat treatment is realized before dialysis process. When encapsulationis realized according to variant 2 of example 1, heat treatment isrealized after the dialysis and resealing process and before washingsteps and addition of NaCl glucose buffer.

The red blood cells are washed several times before being brought to ahaematocrit of 10%. They are then heated for 30 minutes at 48° C.

EXAMPLE 3 Antibody Treatment on the Red Blood Cells Containing Ovalbumin

The suspension of red blood cells encapsulating ovalbumin is washedseveral times before being brought to 10⁹ cells/ml for the in vivo testand 10⁸ cell/ml for the in vitro test. It is incubated with theanti-TER119 antibody (10 μg/ml for the in vitro test and 23 μg/ml or 5μg/ml for the in vivo test) for 30 minutes at 4° C. After a few washes,the final product is taken up in a buffer with injectable qualities, andhaematocrit is brought to 50%.

EXAMPLE 4 Chemical Treatment with Bis(Sulphosuccinimidyl)Suberate (BS3)on the Red Blood Cells Containing Ovalbumin

The suspension of red blood cells encapsulating ovalbumin is washedseveral times before being brought to 1.7×10⁶ cell/μl with PBS and mixedwith one volume of a buffer solution of 2 mM BS3 (the BS3 solutioncontains glucose and phosphate buffer, pH 7.4), so as to obtain a finalBS3 concentration of 1 mM. The cells are incubated for 30 minutes atroom temperature. The reaction is quenched by adding one volume of 20 mMTris-HCl. After incubation at room temperature for 5 minutes, themixture is centrifuged at 800 g for 5 min, 4° C. The cells are thenwashed twice with PBS containing glucose (centrifugation at 800 g) andonce with SAG-mannitol (centrifugation at 1000 g) for 10 min, beforeconstituting the final products.

EXAMPLE 5 Measurement of the Phagocytosis of Ovalbumin-Containing RedBlood Cells by Dendritic Cells In Vitro

The effect of the various treatments (heat and antibody) on thephagocytosis efficiency of the red blood cells obtained according tovariant 1 of example 1, by dendritic cells, is measured in vitro. Thered blood cells are labelled with a fluorescent label, CFSE(carboxyfluorescein succinimidyl ester), for 20 min at 4° C. CFSE is anon-fluorescent dye which diffuses through the cell membrane. Onceinside the cell, the molecule becomes fluorescent subsequent to itscleavage by intracellular esterases.

Dendritic cells are isolated from the spleen of C57Bl/6 mice usingmagnetic beads. These beads carry antibodies which recognize the CD11cmarker, thereby making it possible to isolate the CD11c⁺ dendritic cellfraction.

The CFSE-labelled or unlabelled red blood cells are then incubated withthe dendritic cells (10×10⁶ cell/ml) at a ratio of 20:1 in a finalvolume of 200 μl/well of round-bottomed 96-well culture plates for 4hours at 37° C. and 5% CO₂. After culturing for 4 hours, the red bloodcells not ingested by the dendritic cells are lysed with NH₄Cl, andseveral washes are carried out. The capture of the CFSE fluorochrome bythe dendritic cells is then measured by flow cytometry (R. Segura etal., J. Immunol, January 2006, 176(1): 441-50).

Three populations of red blood cells were tested:

(A) red blood cells loaded with ovalbumin and not labelled with the CFSEfluorochrome,(B) red blood cells loaded with ovalbumin and labelled with CFSE,(C) red blood cells loaded with ovalbumin, treated with the anti-TER 119antibody and labelled with CFSE.

Results

TABLE 1 Percentage of dendritic cells having phagocytosed fluorescentred blood cells: Red blood cell population % of dendritic cells (A)  4%(B) 27% (C) 36%

The murine red blood cells loaded with ovalbumin and treated with theanti-TER 119 antibody were more efficiently phagocytosed by thedendritic cells isolated from the spleen than the untreated red bloodcells in vitro, after 4 hours of coculture (FIG. 1, respectively C andB). 36% of the dendritic cells phagocytosed the red blood cells carryingthe antibody, against only 27% in the absence of antibody. Phagocytosisof the antibody-treated red blood cells by a population not expressingthe CD11c dendritic cell marker was also observed (10.9%; FIG. 1, C).

EXAMPLE 6 Measurement of the Phagocytosis of Red Blood Cells ContainingOvalbumin, by Macrophages and Dendritic Cells of the Spleen and Liver InVivo on Mice

This study is an allogenic study since OF1 mice red blood cellscontaining ovalbumin are injected to not consanguineous C57Bl/6 mice.

Three batches of 74×10⁷ red blood cells, from OF1 mice, loaded withovalbumin (variant 1 of example 1) heat treated, treated with theanti-TER 119 antibody (as described in examples 2 and 3, respectively)or not treated are prepared. These batches are divided up in thefollowing way:

Batch 1: no heat or antibody treatment (FIGS. 2, A and D)Batch 2: heat treated (FIGS. 2, B and E)Batch 3: treated with the anti-TER 119 antibody (FIGS. 2, C and F).

Each batch is labelled with CFSE and injected intravenously into C57Bl/6mice. Three hours after the injection, the blood, the spleen and theliver of the mice are taken. The percentage of fluorescent red bloodcells circulating in the blood of the mice is measured by flowcytometry. The fluorescence incorporated into the spleen macrophagesexpressing the F4/80 marker (FIG. 2, A, B, C), into the livermacrophages expressing the F4/80 marker and into the spleen dendriticcells expressing the CD11c marker (FIG. 2, D, E, F) is measured by flowcytometry.

Results

TABLE 2 Percentage of macrophages or dendritic cells from the spleen,having phagocytosed fluorescent red blood cells 3 hours after injectioninto the mouse: Batches Macrophages Dendritic cells 1 28%  5% 2 68% 19%3 81% 22%

3 hours after injection, the murine red blood cells loaded withovalbumin and heat-treated or treated with the anti-TER 119 antibody arealmost no longer present in the blood of the mouse (1.6% and 1%),whereas there are still untreated, ovalbumin-loaded red blood cells inthe blood of the mouse (4.6%).

The red blood cells that have been heat-treated or treated with theanti-TER 119 antibody are phagocytosed by the F4/80 macrophages andCD11c dendritic cells of the spleen (FIG. 2).

The red blood cells treated with the anti-TER 119 antibody were moreefficiently phagocytosed by the F4/80 macrophages of the spleen than theheat-treated red blood cells or the untreated red blood cells (FIG. 2,A, B, C). 81% of the spleen macrophages phagocytosed theantibody-treated red blood cells, against 68% of macrophages havingphagocytosed the heat-treated red blood cells and only 28% in theuntreated batch (Table 2).

The heat-treated or antibody-treated red blood cells were also moreefficiently phagocytosed by the CD11c dendritic cells from the spleenthan the untreated red blood cells (FIG. 2). Respectively 22% and 19% ofdendritic cells phagocytosed the antibody-treated red blood cells andthe heat-treated red blood cells, against only 5% in the case of theuntreated red blood cells (Table 2).

Phagocytosis of the antibody-treated red blood cells by a populationfrom the spleen not expressing the CD11c dendritic cell marker or theF4/80 macrophage marker was also observed (11.9% and 12.8%, FIG. 2).

TABLE 3 Percentage of liver macrophages having phagocytosed fluorescentred blood cells 3 hours after injection into the mouse. BatchesMacrophages 1 24% 2 40% 3 50%

The heat-treated red blood cells or the red blood cells treated with theanti-TER 119 antibody are phagocytosed by the F4/80 macrophages of theliver.

The red blood cells treated with the anti-TER 119 antibody were moreefficiently phagocytosed by the F4/80 macrophages of the liver than theheat-treated red blood cells or than the untreated red blood cells. 50%of the liver macrophages phagocytosed the antibody-treated red bloodcells, against 40% of macrophages having phagocytosed the heat-treatedred blood cells and only 24% in the untreated batch (table 3).

In conclusion, the binding of the antibody to the red blood cells andthe heat treatment allowed efficient targeting of the red blood cells inthe spleen and the liver, and a significant increase in the percentageof dendritic cells and of macrophages capable of phagocytizing these redblood cells.

EXAMPLE 7 Measurement of the Phagocytosis of Mouse Red Blood CellsContaining Fluorescent Ovalbumin by Bone Marrow Macrophages andDendritic Cells In Vivo

This study is an autologous study, since OF1 mouse red blood cells areinjected into OF1 mice.

Four batches of 132×10⁷ OF1 mouse red blood cells loaded withfluorescent ovalbumin (Serlabo Technologies, ref WO-LS003054) preparedusing variant 2 of example 1 and treated with the anti-TER 119 antibody,with heat or with BS3 (as described in Examples 3, 2 and 4,respectively) or not treated are prepared. Each batch of red blood cellsis injected intravenously into two mice. One and a half hours after theinjection, the mice are sacrificed and the femurs of the mice areremoved. The fluorescence incorporated into the macrophages expressingthe F4/80 marker or the CD11b marker, the granulocytes expressing theGr1 marker, the myeloid dendritic cells expressing the CD11c and CD11bmarkers and into the plasmacytoid dendritic cells expressing the CD11cand CD8 markers is measured by flow cytometry.

Batch 1: ovalbumin-loaded red blood cells, treated with BS3Batch 2: ovalbumin-loaded red blood cells, heat-treatedBatch 3: ovalbumin-loaded red blood cells, treated with the anti-TER 119antibodyBatch 4: ovalbumin-loaded red blood cellsBatch 5: NaCl glucose

Results

TABLE 4 Percentage of bone marrow macrophages, granulocytes or dendriticcells having phagocytosed fluorescent ovalbumin 1 hour 30 min after theinjection: F4/80 CD11b Granu- Myeloid Plasmacytoid Batches macrophagesmacrophages locytes dendritic dendritic 1 2.5 0.05 12.5 2.7 2.4 2 3.3 015.5 2.2 3.4 3 17.7 1.75 21 15.3 6 4 2.4 0 13 1.6 2.4 5 0.5 0.1 1.3 0.81.5

One and a half hours after injection, the ovalbumin-loaded red bloodcells treated with the anti-TER 119 antibody were efficientlyphagocytosed by the F4/80 macrophages, the granulocytes and thedendritic cells of the bone marrow. The myeloid dendritic cells of thebone marrow are the cells most involved in the phagocytosis of theovalbumin-loaded red blood cells treated with the anti-TER 119 antibody.

In conclusion, the use of red blood cells treated with the anti-TER 119antibody allows the best targeting and phagocytosis of the red bloodcells by immune cells in the bone marrow.

EXAMPLE 8 Measurement of the Ovalbumin-Specific CD4 T Cell Responseafter a Single Injection of Ovalbumin-Loaded Red Blood Cells and ofPoly(I:C) Adjuvant

The evaluation of the OVA (ovalbumin)-specific CD4 T cell responseconsists in measuring the percentage of OVA-specific CD4 T cells, theproliferation of these cells, the level of activation of these cells andthe production of IFNg (g=gamma).

The evaluation of the CD4 T cell response is realized using anadaptation of the methods described in Russo V. et al. The Journal ofClinical Investigation, 2007, 117: 3087-3096; Stoitzner P. et al., TheJournal of Immunology 2008, 180: 1991-1998. The CD4 T cells of OT-IItransgenic mice (Charles River, ref C57BL/6-Tg(TcraTcrb425Cbn/Crl)) areused to measure the OVA-specific CD4 T cell response. The OT-II mice aremice expressing only CD4 T cells which recognize the ovalbumin peptide323-339 associated with major histocompatibility complex class IImolecules.

The OT-II transgenic CD4 T cells are isolated from the spleen of OT-IImice and labelled with CFSE, before being injected intravenously intoLy5.1 mice. OT-II mice and Ly5.1 mice have the same genetic background,but the cells of both types of mice can be identified by means of theCD45 marker. This is because the cells of OT-II mice express the CD45.2marker, whereas the Ly5.1 mice express the CD45.1 marker.

20 hours after the injection of the transgenic mouse CD4 T cells, theLy5.1 mice receive an intravenous injection of the following batches.Three mice are injected with the batches containing red blood cells andtwo mice are injected with the batches containing free OVA or thecontrol.

Two batches of 183×10⁷ red blood cells of C57Bl/6 mice loaded withovalbumin (Serlabo Technologies, ref WO-LS003054) prepared using variant2 of example 1 and treated or not with the anti-TER 119 antibody (asdescribed in example 3) are prepared. The adjuvant, Poly (I:C)(Invivogen, ref tlrl-pic), is added to these batches, as well as to thebatch containing free ovalbumin. The amount of Poly (I:C) injected permouse is 25 μg. The amount of OVA injected into the mice is indicated inTable 5.

This is an autogenic study since ovalbumine-loaded C57Bl/6 mice redblood cells are injected to Ly5.1 mice. C57Bl/6, Ly5.1 and OT-II micehave the same genetic background.

Batch 1: Poly (I:C) and ovalbumin-loaded red blood cells treated withthe anti-TER 119 antibodyBatch 2: Poly (I:C) and ovalbumin-loaded red blood cellsBatch 3: Poly (I:C) and free ovalbumin

Batch 4: Plasma

Three days after the injection of the batches, the mice are sacrificedand the spleens of the mice are removed. The percentage of OVA-specificCD4 T cells in the spleen of the mice is measured by flow cytometryusing the CD4 and CD45.2 markers (Table 5). The number of OVA-specificCD4 T cells is calculated from the percentage of OVA-specific CD4 Tcells and the number of total lymphocytes counted with trypan blue(Invitrogen, ref 15250061) (Table 5).

The proliferation and the activation of the OVA-specific CD4 T cells inthe spleen of the mice is measured by flow cytometry using the CD4, CD44and CD45.2 markers and using CFSE (Tables 6 and 7). At each celldivision, the amount of CFSE contained in the OVA-specific CD4 T cellsis divided by a factor of 2, which makes it possible to determine thenumber of cell divisions by flow cytometry (FIG. 3).

The production of IFNg by the mice splenocytes is measured in theculture supernatants after 3 days of in vitro stimulation in thepresence of 10 μg/ml of ovalbumin peptide 323-339 (Neomps, ref) by meansof an ELISA assay.

Results

TABLE 5 Percentage and number of OVA-specific CD4 T cells three daysafter injection of the batches (mean ± standard deviation): Amount ofOVA % of Number of OVA-specific injected into OVA-specific CD4 T cellsBatches the mice (μg) CD4 T cells (millions of cells) 1 160  6.6 ± 1.4* 8 ± 2* 2 129  3.6 ± 0.9** 4.1 ± 2*  3 150 0.8 ± 0.3 1.3 ± 0.7 4 0 0.1 ±0.1 0.2 ± 0.1

Three days after injection of the batches, the mice injected with Poly(I:C) and ovalbumin-loaded red blood cells treated or not with theanti-TER 119 antibody have a significantly higher percentage and numberof OVA-specific CD4 T cells than the mice injected with free OVA andPoly (I:C) (Student test *p=0.01, **p=0.02).

Furthermore, the batch containing ovalbumin-loaded red blood cellstreated with the anti-TER 119 antibody is more effective in inducing anincrease in the number of OVA-specific CD4 T cells than the batchcontaining untreated, ovalbumin-loaded red blood cells (Student testp=0.04).

TABLE 6 Percentage of OVA-specific CD4 T cells which have divided 0, 1,2, 3, 4, 5, 6 or 7 times three days after injection of the batches: % ofOVA-specific CD4 T cells at each division cycle (mean ± standarddeviation) Batches 0 1 2 3 4 5 6 7 1  0 ± 0 0 ± 0 0.1 ± 0  0.3 ± 0  1.7± 0   9.4 ± 0.1 35.9 ± 0.3  52.5 ± 0.2 2 0.1 ± 0  0.1 ± 0   0.2 ± 0  0.8 ± 0.1  4.2 ± 0.8 19.2 ± 3.2 43.7 ± 2.2  31.5 ± 6.3 3  1.9 ± 1.4 6.9± 5.2 15.6 ± 9.5 18.7 ± 5.6 19.7 ± 0.4 16.4 ± 5.3 13.9 ± 10.1  6.8 ± 5.94 69.7 ± 4.9 1.3 ± 1    0.1 ± 0.2  0.3 ± 0.4  5.6 ± 3.7  3.7 ± 1.1 5.3 ±2.8 13.6 ± 2.5

These observations are confirmed by the in vivo cell proliferationresults (Table 6 and FIG. 3). Cell division induces a decrease of theCFSE fluorescence intensity: disparition of half of the fluorescentmaterial at each division (FIG. 3A). The OVA-specific CD4 T cells dividemore rapidly (Table 6 and FIG. 3A) for the mice injected with Poly (I:C)and ovalbumin-loaded red blood cells treated with the anti-TER 119antibody (6 to 7 divisions) in comparison with the mice injected withfree OVA and Poly (I:C) (3 to 4 divisions). Furthermore, the batchcontaining ovalbumin-loaded red blood cells treated with the anti-TER119 antibody appears to be more effective in inducing cell proliferationthan the batch containing untreated, ovalbumin-loaded red blood cells.

TABLE 7 Level of activation of OVA-specific CD4 T cells three days afterinjection of the batches: Mean of OVA-specific CD4 T cells activationBatche fluorescence (mean ± standard deviation) 1 32.6 ± 2.3 2 37.6 ±3.5 3 34.6 ± 3.9 4 11.4 ± 0.5

The results of the cell activation level (characterized by the level ofexpression of the CD44 marker) show that all the dividing OVA-specificCD4 T cells have a high cell activation level (Table 7 and FIG. 3). Inaddition, the activation level of the OVA specific CD4 T cells can becorrelated to the number of divisions of these cells: the more the cellshave divided and have lost their CFSE marker content, the more theyexpress a high level of activation marker (FIG. 3B).

TABLE 8 Production of IFNg by splenocytes stimulated in vitro with 10μg/ml of ovalbumin peptide 323-339 for 3 days: Production of IFNg bysplenocytes in ng/ml Batches (mean ± standard deviation) 1 56.3 2  60 ±26.8 3 9.4 ± 1.6 4 6.7 ± 1 

The results of IFNg production by splenocytes show a strong productionof IFNg by the splenocytes of mice injected with Poly (I:C) andovalbumin-loaded red blood cells treated or not treated with theanti-TER119 antibody.

In conclusion, these results demonstrate the superiority of theovalbumin-loaded red blood cells treated or not with the anti-TER 119antibody, on the activation and proliferation of OVA-specific CD4 Tcells capable of producing IFNg.

EXAMPLE 9 Measurement of the Ovalbumin-Specific CD8 T Cell Responseafter a Single Injection of Ovalbumin-Loaded Red Blood Cells and of Poly(I:C) Adjuvant

The evaluation of the OVA-specific CD8 T cell response consists inmeasuring the percentage of OVA-specific CD8 T cells, the production ofIFNg and the cell lysis, in vivo, of the cells presenting the ovalbuminpeptide 257-264 associated with major histocompatibility complex class Imolecules. This study is an allogenic study, since ovalbumin-loaded redblood cells from OF1 mice are injected into not consanguineous C57Bl/6mice.

Two batches of 167×10⁷ ovalbumin-loaded OF1 mouse red blood cellsprepared using variant 2 of example 1 and treated or not with theanti-TER 119 antibody (as described in example 3) are prepared. Theadjuvant, Poly (I:C), is added to these batches, and also to the batchcontaining free ovalbumin. The amount of Poly (I:C) injected per mouseis 25 μg. The amount of OVA injected into the mice is indicated in Table9.

The batches are injected intravenously into C57Bl/6 mice. A minimum of 4mice are injected with a given batch. In vivo cell lysis is measuredusing an adaptation of the method described by Hervas-Stubbs S. et al.,Blood 2007, 109: 5318-5326. Cells presenting the ovalbumin peptide257-264 associated with major hisotocompatibility complex class Imolecules are injected into the immunized mice. Briefly, six days afterthe injection, the mice receive an injection of 0.5×10⁶ splenocytespresenting the ovalbumin 257-264 peptide (Neomps, ref SC1302) andlabelled with a moderate concentration of CFSE, and of 0.5×10⁶splenocytes not presenting the peptide and labelled with highconcentrations of CFSE (cell lysis control).

Latex beads coupled to ovalbumine peptide 257-264 (BOVAp) and poly(I:C)are used as positive control to induce a CD8 T immune response againstovalbumine. It has been shown that the injection of BOVAp and ofpoly(I:C) induces an incease of the percentage of ovalbumine-specificCD8 T cells and the destruction of cells presenting the OVA257-264peptide in vivo (Herva-Stubbs).

Batch 1: Poly (I:C) and ovalbumin-loaded red blood cells treated withthe anti-TER 119 antibodyBatch 2: Poly (I:C) and ovalbumin-loaded red blood cellsBatch 3: Latex beads coupled to the ovalbumin peptide 257-264Batch 4: Poly (I:C) and latex beads coupled to the ovalbumin peptide257-264Batch 5: Poly (I:C) and free ovalbuminBatch 6: NaCl glucose+plasma

16 hours after injection of the splenocytes, the mice are sacrificed byeuthanasia and the spleens of the mice are removed. The percentage ofOVA-specific CD8 T cells in the spleen of the mice is measured by flowcytometry using tetramer and the CD8 marker (Table 9). IFNg productionand expression of the marker associated with degranulation (CD107) byCD8 T cells was measured by flow cytometry after in vitro stimulationfor 4 hours in the presence of 0.1 μg/ml of ovalbumin peptide 257-264(Table 10). In vivo cell lysis was measured by flow cytometry using CFSE(Table 11).

Results

TABLE 9 Percentage of OVA-specific CD8 T cells seven days afterinjection of batches (mean ± standard deviation): % of OVA-specific % ofOVA-non- Quantity of OVA CD8 T cells specific T cells injected into(mean ± standard (mean ± standard Batch mice (μg) deviation) deviation)1 95  14 ± 3.2* 2.4 ± 0.2 2 91  12.5 ± 5.2** 1.2 ± 0.5 3 0 1.2 ± 0.1 1.2± 0.1 4 0  2.5 ± 0.4* 0.9 ± 0.1 5 130 2.4 ± 1.4  1 ± 0.2 6 0 0.7 ± 0.4 1 ± 0.1

Mice injected with Poly(I:C) and ovalbumin-charged red blood cells whichhad either been treated or had not been treated with anti-TER119antibody have a significantly higher percentage of OVA-specific CD8 Tcells than mice injected with free OVA and Poly(I:C) or mice injectedwith Poly(I:C) and BOVAp (Student's test: *p=0.001 and **p=0.01).

TABLE 10 Production of IFNg by CD8 T cells stimulated in vitro with 0.1μg/ml of ovalbumin peptide 257-264 for 4 hours: % of CD8 T cells % CD8 Tcells producing IFNg and Batch producing IFNg expressing CD107 marker 1 8.7 ± 1.8* 71 ± 4* 2  6.6 ± 1.7* 71 ± 4* 3 1.4 ± 0.1  33 ± 4.5 4 2.8 ±0.5  57 ± 5.5 5 1.8 ± 0.5 46 ± 7  6 0.7 ± 0.1 18 ± 2 

The CD8 T cells generated are effective and cytotoxic since they produceIFNg and express the CD107 marker in response to stimulation with theovalbumin peptide (Table 10). The percentage of CD8 T cells producingIFNg and expressing CD107 is significantly higher for mice injected withPoly(I:C) and ovalbumin-charged red blood cells which had either beentreated or had not been treated with anti-TER119 antibody than for miceinjected with free OVA and Poly(I:C) or Poly(I:C) and BOVAp (Student'stest, p<0.008).

TABLE 11 Percentage of in vivo anti-OVA-specific cell lysis (mean ±standard deviation): % cell lysis, in vivo Batch (mean ± standarddeviation) 1 82 ± 7 2 83 ± 4 5 53 ± 8 6 0

The cell lysis results correlate with expression of the markerassociated with degranulation (Tables 10 and 11). Injection of Poly(I:C)and ovalbumin-charged red blood cells which had either been treated orhad not been treated with anti-TER119 antibody induced lysis of cellsdisplaying ovalbumin peptide 257-264 in a manner which was moreeffective than injection of Poly(I:C) and free ovalbumin (Table 10).

In conclusion, these results demonstrate the superiority ofovalbumin-charged red blood cells which have either been treated or havenot been treated with anti-TER119 antibody in the activation andproliferation of cytotoxic CD8 T cells capable of producing IFNg,degranulating and lysing cells displaying ovalbumin peptide 257-264.

EXAMPLE 10 Measuring the Maintenance of the Ovalbumin-Specific CD8 TCell Response 30 Days after a Single Injection of Ovalbumin-Charged RedBlood Cells and Adjuvant Poly(I:C)

Evaluating the maintenance of the OVA-specific CD8 T cell responseconsisted of measuring the percentage of OVA-specific CD8 T cells andcell lysis in vivo 34 days after a single injection.

This study was an allogenic study, since red blood cells charged withOF1 mouse ovalbumin were injected into non-consanguineous C57Bl/6 mice.

Two batches were prepared of 150×10⁷ of ovalbumin-charged OF1 mouse redblood cells obtained in accordance with variant 2 of Example 1 which hador had not been treated with anti-TER119 antibody (as described inExample 3). The adjuvant, Poly(I:C), was added to these batches, andalso to the batch containing free ovalbumin or BOVAps. The quantity ofPoly(I:C) injected per mouse was 25 μg. The quantity of OVA injectedinto the mice is shown in Table 12.

The batches were injected intravenously into C57Bl/6 mice. Three micewere injected with a given batch. To measure cell lysis in vivo, cellsdisplaying ovalbumin peptide 257-264 associated with molecules of themajor histocompatibility complex of class I were injected into immunizedmice. 33 days after injection, the mice received an injection of 0.5×10⁶splenocytes displaying ovalbumin peptide 257-264 (NeoMPS, referenceSC1302) and labelled with a moderate concentration of CFSE and of0.5×10⁶ splenocytes not displaying the peptide and labelled with a highconcentration of CFSE (cell lysis assay).

-   Batch 1: Poly(I:C) and ovalbumin-charged red blood cells, treated    with anti-TER119 antibody-   Batch 2: Poly(I:C) and ovalbumin-charged red blood cells-   Batch 3: Latex beads coupled with ovalbumin peptide 257-264: BOVAp-   Batch 4: Poly(I:C) and BOVAp-   Batch 5: Poly(I:C) and free ovalbumin-   Batch 6: NaCl glucosated+plasma

16 hours after injecting the splenocytes, the mice were euthanized andtheir spleens were removed. The percentage of OVA-specific CD8 T cellsin the spleens of the mice was measured by flow cytometry using tetramerand CD8 marker (Table 12). In vivo cell lysis was measured by flowcytometry using CFSE (Table 13).

TABLE 12 Percentage of OVA-specific CD8 T cells 34 days after injectionof batches (mean ± standard deviation) Quantity of OVA % of OVA-specificCD8 injected into T cells (mean ± Batch mice (μg) standard deviation) 1170 1.5 ± 0.2 2 138 1.7 ± 0.3 3 0 1.6 ± 0.1 4 0 1.4 ± 0.1 5 150 2.2 ±0.2 6 0  1.8 ± 0.06

34 days after injection, the percentage of OVA-specific CD8 T cells wasequivalent for each group (Table 12). This result is not surprisinggiven that the peak CD8 T cell proliferation was at about day 7 and itwas followed by a contraction phase (Hervas-Stubbs S et al, Blood, 2007,109: 5318-5326).

TABLE 13 Percentage of anti-OVA-specific cell lysis in vivo (mean ±standard deviation): % cell lysis in vivo Batch (mean ± standarddeviation) 1 49 ± 9* 2 54 ± 28 3  12 ± 5.4 4 21.6 ± 12  5 20.4 ± 19  60.9 ± 0.9

34 days after injection, the OVA-specific CD8 T cells were still capableof lysing cells displaying ovalbumin peptide 257-264 (Table 13).Injection of Poly(I:C) and ovalbumin-charged red blood cells treatedwith anti-TER119 antibody induced cell lysis in a manner which was moreeffective than injection of Poly(I:C) and BOVAp (Student's test,p<0.04).

In conclusion, these results demonstrate that ovalbumin-charged redblood cells are superior not only as regards activation andproliferation of cytotoxic CD8 T cells, but also as regardsmaintenance/survival of these T cells which are capable of lysing cellsdisplaying ovalbumin peptide 257-264.

EXAMPLE 11 Measurement of the Ovalbumin-Specific CD8 T Cell Responseafter a Single Injection of Chemically Treated, Ovalbumin-Loaded RedBlood Cells and of Poly (I:C) Adjuvant

This study is an allogenic study, since ovalbumin-loaded red blood cellsfrom OF1 mice are injected into not consanguineous C57Bl/6 mice.

A batch of 132×10⁷ ovalbumin-loaded OF1 mouse red blood cells preparedusing variant 2 of example 1 and chemically treated with 1 mM BS3 (asdescribed in example 4) is prepared. The adjuvant Poly (I:C), is addedto this batch, and to the batch containing free ovalbumin. The amount ofPoly (I:C) injected per mouse is 25 μg. The amount of OVA injected intothe mice is indicated in Table 14.

Batch 1: Poly (I:C) and ovalbumin-loaded red blood cells treated with 1mM BS3Batch 2: Poly (I:C) and free ovalbumin

Batch 3: Poly (I:C)

Batch 4: NaCl containing glucose

The batches are injected intravenously into C57Bl/6 mice. A minimum of 3mice are injected with a given batch. Seven days after the injection,the mice are sacrificed and the spleens of the mice are removed. Thepercentage of OVA-specific CD8 T cells in the spleen of the mice ismeasured by flow cytometry using tetramer and the CD8 marker (Table 14).

Results

TABLE 14 Percentage and number of OVA-specific CD8 T cells seven daysafter injection of the batches (mean ± standard deviation): Amount ofOVA injected % of OVA-specific CD8 T cells Batche into the mice (mean ±standard deviation) 1 38 1.8 ± 0.6 2 150 1.2 ± 0.3 3 0 1± 4 0 0.8 ± 0.1

The mice injected with Poly (I:C) and ovalbumin-loaded red blood cellstreated with BS3 have a higher percentage of OVA-specific CD8 T cellsthan the mice injected with free OVA and Poly (I:C) or than the miceinjected with Poly (I:C). These results are not statistically different,but it should be noted that the amount of free OVA injected is more thanthree times greater than the amount of OVA injected in the batchcontaining the OVA-loaded red blood cells.

In conclusion, these results show that the ovalbumin-loaded red bloodcells treated with BS3 are also capable of generating OVA-specific CD8 Tcells.

EXAMPLE 12 Measurement of the Ovalbumin-Specific CD8 T Cell Responseafter a Single Injection of Ovalbumin-Loaded Red Blood Cells and ofCL-097 Adjuvant

This study is an allogenic study, since ovalbumin-loaded red blood cellsfrom OF1 mice are injected into not consanguineous C57Bl/6 mice.

Batches of 119×10⁷ ovalbumin-loaded OF1 mouse red blood cells preparedusing variant 1 of example 1 and treated or not with the anti-TER 119antibody (as described in example 3) are prepared. The adjuvant, CL097(Invivogen, ref tlrl-c97), is or is not added to these batches. Theamount of CL097 injected per mouse is 0.15 μg. The amount of OVAinjected into the mice is indicated in Table 15.

Batch 1: CL097 and ovalbumin-loaded red blood cells treated with theanti-TER 119 antibodyBatch 2: ovalbumin-loaded red blood cells treated with the anti-TER 119antibodyBatch 3: CL097 and ovalbumin-loaded red blood cellsBatch 4: ovalbumin-loaded red blood cellsBatch 5: NaCl containing glucose

The batches are injected intravenously into C57Bl/6 mice. Four daysafter the injection, the mice are sacrificed and the spleens of the miceare removed. The IFNg production by the splenocytes of mice injectedwith the various batches is measured in the culture supernatants afterthree days of in vitro stimulation in the presence of 0.1 μg/ml ofovalbumin peptide 257-264 by means of ELISA assay.

Results

TABLE 15 IFNg production by splenocytes stimulated in vitro with 0.1μg/ml of ovalbumin peptide 257-264 for 3 days: Amount of OVA injectedIFNg production by splenocytes Batche into the mice (μg) in ng/ml 1 8315. 2 83 5.7 3 103 11. 4 103 7.4 5 0 0.4

The results of IFNg production by the splenocytes show a greater IFNgproduction when the mice received an injection of both the CL097adjuvant and ovalbumin-loaded red blood cells treated or not with theanti-TER 119 antibody.

In conclusion the CL097 adjuvant also potentiates the IFNg responseinduced by the injection of the ovalbumin-loaded red blood cells.

EXAMPLE 13 Measure of Tumoral Growth after One Injection of AdjuvantPoly (I:C) and Treated or Untreated Ovalbumin-Loaded Erythrocytes inMice

The purpose of this study is to measure the tumor growth of EG.7 cellline in C57Bl/6 mice after injection of a single dose of Poly (I:C) andtreated or untreated ovalbumin-loaded erythrocytes. EG.7 tumor cells areobtained from ATCC (ATCC-CRL-2113). EG.7 cells originate from the EL.4cell line, which synthesize and secrete OVA constitutively.

This is an allogenic study since ovalbumin-loaded erythrocytes from OF1mice are injected into C57Bl/6 mice. The model in this experiment is aprophylactic model.

Two batches of 165×10⁷ antibody-treated or untreated ovalbumin-loadederythrocytes from OF1 mice are prepared according to variant 2 ofexample 1. The adjuvant, Poly (I:C), is added to those batches. 25 μg ofPoly (I:C) is injected per mice. The negative control is a suspension ofunloaded erythrocytes. OVA amounts injected to mice are indicated intable 16.

Batch 1: Poly (I:C) and antibody-treated ovalbumin-loaded erythrocytesBatch 2: Poly (I:C) and ovalbumin-loaded erythrocytesBatch 3: unloaded erythrocytes

The batches are injected intravenously to C57Bl/6 mice (10 mice pergroup). Seven days after batch injection, 2.2×10⁶ EG.7 cells per miceare injected subcutaneously. Mice are followed for tumor growth. Tumorgrowth is assessed by measuring the diameter of the tumor in centimeters(recorded as the average of two perpendicular diameter measurements).Tumor size is measured 3 times per week at 2 days interval during 14days. Mice with tumors of more than 2.0 cm of diameter are killed.

TABLE 16 OVA amount injected per mice Batches OVA quantity injected tomice (μg) 1 134 2 134 3 0

TABLE 17 Tumor growth Tumor growth (mm³) the days following tumor cellinjection Batches 0 3 5 7 10 12 14 1 0 0 0 0 0 0 0 2 0 0 0 0 0 0 0 3 0 00 363 ± 200 756 ± 462 1009 ± 445 1198 ± 541

7 days after EG.7 injection, the size of the tumors is measurable on theflank of the mice previously injected with unloaded erythrocytes and thetumors continue to growth until the end of the study. Whereas no tumorsare observed on the flank of the mice injected with Poly (I:C) andovalbumin-loaded red blood cells treated or not with the anti-TER 119antibody. Observation of the mice is still ongoing.

In conclusion, these results demonstrate that ovalbumin-loaded red bloodcells treated or not with the anti-TER 119 antibody are efficient toprevent the growth of OVA expressing tumor cells.

EXAMPLE 14 Measurement of the Phagocytosis of Pig Red Blood Cells byMacrophages and Dendritic Cells In Vivo

This study is a xenogenic study, since pig red blood cells are injectedinto C57Bl/6 mice.

The pig red blood cells are washed three times in NaCl containingglucose, before being labelled with CFSE as described above. The redblood cells are washed again three times in NaCl containing glucose, andthen brought back to a haematocrit of 50%. A batch of 142×10⁷ pig redblood cells is injected intravenously into three C57Bl/6 mice. One hourafter the injection, the mice are sacrificed and the spleens, the liversand the femurs of the mice are removed. The fluorescence incorporatedinto the macrophages expressing the F4/80 marker or the CD11b marker,into the myeloid dendritic cells expressing the CD11c and CD11b markersand into the plasmacytoid dendritic cells expressing the CD11c and CD8markers is measured by flow cytometry.

Batch 1: pig red blood cellsBatch 2: NaCl containing glucose

Results

TABLE 18 Percentage of spleen macrophages or dendritic cells havingphagocytosed fluorescent red blood cells 1 hour after injection: F4/80CD11b Myeloid Plasmacytoid Batches macrophages macrophages dendriticcells dendritic cells 1 27 ± 6 4 ± 2 21 ± 5.5 45 ± 6 2 0 1 4 3

TABLE 19 Percentage of bone marrow macrophages or dendritic cells havingphagocytosed fluorescent red blood cells 1 hour after injection: F4/80CD11b Myeloid Plasmacytoid Batches macrophages macrophages dendriticcells dendritic cells 1 5.3 ± 7.5 0.8 ± 1 5 ± 3 5 ± 7 2 6.3 0 6 12.9

TABLE 20 Percentage of liver macrophages or dendritic cells havingphagocytosed fluorescent red blood cells 1 hour after injection: CD11bMyeloid Plasmacytoid Batche macrophages dendritic cells dendritic cells1 1.1 ± 1.1 3±  1.2± 2 1.7 3.4 0.7

One hour after injection, the pig red blood cells were efficientlyphagocytosed by the F4/80 macrophages and the dendritic cells of thespleen (Table 18). The plasmacytoid dendritic cells of the spleen arethe cells most involved in the phagocytosis of the pig red blood cells.In the bone marrow and the liver, the macrophages and the dendriticcells did not phagocytize fluorescent red blood cells (Tables 19 and20).

In conclusion, the use of pig red blood cells allows targeting andphagocytosis of the red blood cells by the spleen cells involved in thegeneration of immune responses (Lou Y., 2007, J of Immunol, 178:1534-1541).

EXAMPLE 15 Characteristics of Pig Red Blood Cells Comprising Ovalbumin

Two batches were prepared of pig red blood cells which had either beencharged with ovalbumin (obtained in accordance with variant 2 ofExample 1) or had not been charged therewith.

Batch 1: Pig red blood cells charged with OVABatch 2: Pig red blood cells not charged with OVA.

Batches from the starting material were characterized at the end ofproduction and 18 hours after production. The mean globular volume, themean corpuscular haemoglobin and the concentration of red blood cellswas measured using an ABX cell counter. The osmotic fragility, whichcorresponds to the concentration of NaCl inducing 50% haemolysis of redblood cells, was measured using an Osmocells instrument (SD Medical).The extracellular haemoglobin was measured by spectrophotometry. Thecorpuscular concentration of ovalbumin, the extracellular concentrationof ovalbumin and the mean globular quantity of ovalbumin were determinedusing an ELISA test.

TABLE 21 Characteristics of pig red blood cells comprising ovalbumin:Day of production 18 hours after production Starting Batch BatchStarting Batch Batch Characteristics material 1 2 material 1 2 Meanglobular 65 55 57 65 56.0 58 volume (μm³) Mean 31.9 27.7 25.9 31.4 28.925.8 corpuscular haemoglobin (g/dl) Osmotic 3.98 2.51 3.33 fragility(salinity inducing 50% haemolysis in g/l of NaCl) Haematocrit of 36.848.2 50 36.5 46.3 48 suspension (%) Concentration 5.64 9.1 8.1 5.9 9 8.4of red blood cells (10⁶/mm³) Extracellular 0.04 0.27 0.196 0.05 0.790.56 haemoglobulin (g/dl) Corpuscular 0.66 0 0.71 0 ovalbuminconcentration (mg/ml of red blood cells) Extracellular 0.02 0 0.02 0ovalbumin concentration (mg/ml of end product) Mean globular 0.03 0 0.040 quantity (mg/10⁹ GR)

As expected, the dialysis procedure caused a reduction in the globularvolume and the corpuscular haemoglobin. Furthermore, the osmoticfragility of the batches was lower than that of the red blood cells ofthe initial blood (Table 21). No major differences were observed betweenthe batch comprising the ovalbumin (batch 1) and that which did notcomprise it (batch 2).

For batch 1, the quantity of extracellular ovalbumin was relatively lowcompared with the quantity of encapsulated ovalbumin and had notincreased 18 hours after production, thereby demonstrating the stabilityof the red blood cells encapsulating the ovalbumin.

Thus, it is possible to encapsulate ovalbumin in pig red blood cells.

1. Composition which induces, in a host, a cytotoxic cellular responseagainst tumour cells, and which comprises red blood cells containing atumour antigen.
 2. Composition according to claim 1, wherein the redblood cells (1) contain an antigen and (2) are in the form of an immunecomplex with an immunoglobulin which recognizes an epitope at thesurface of the red blood cells, so as to promote phagocytosis of saidred blood cells by dendritic cells.
 3. Composition according to claim 2,wherein the red blood cells form an immune complex with an anti-rhesusor anti-glycophorin A or anti-CR1 antibody.
 4. Composition according toclaim 2, wherein the immunoglobulin is an IgG.
 5. Composition accordingto claim 1, wherein the red blood cells (1) contain an antigen and (2)are heat-treated or chemically treated so as to promote phagocytosis ofsaid red blood cells by dendritic cells.
 6. Composition according toclaim 2 wherein the red blood cells in the form of an immune complex areheat-treated or chemically treated.
 7. Composition according to claim 1,wherein the red blood cells are xenogenic red blood cells. 8.Composition according to claim 1, which further comprises an adjuvantfor activating dendritic cell maturation.
 9. Composition according toclaim 8, wherein the adjuvant is present in the red blood cells, attheir surface and/or outside the red blood cells.
 10. Compositionaccording to claim 9, wherein the adjuvant is a TLR (Toll-like receptor)ligand or a cytokine.
 11. Composition according to claim 10, wherein theTLR ligand is selected from imidazoquinolines belonging to the groupconsisting of imidazoquinoline, imiquimod, resiquimod, CpGoligodeoxynucleotides LPSs (lipopolysaccharides) or poly(inosinicacid)-poly(cytidylic acid).
 12. Composition according to claim 10,wherein the cytokine is selected from the group consisting of interferonalpha, IL-2 (interleukin 2), IFNγ (interferon gamma), GM-CSF(Granulocyte Monocyte-Colony Stimulating Factor), IL-12 (interleukin 12)or TNFα (Tumor Necrosis Factor alpha).
 13. Composition according toclaim 1, comprising at least two tumour antigens representative of thetumour to be treated.
 14. Composition according to claim 1, wherein thetumour antigen is selected from the group consisting of the followingantigens: alpha-actinin-4; ARTC1; BCR-ABL fusion protein (b3a2); B-RAF;CASP-5; CASP-8; beta-catenin; Cdc27; CDK4; CDKN2A; COA-1; dek-can fusionprotein; EFTUD2; Elongation factor 2; ETV6-AML1 fusion protein; FN1;GPNMB; LDLR-fucosyltransferaseAS fusion protein; HLA-A2d; HLA-A11d;hsp70-2; KIAAO205; MART2; ME1; MUM-1f; MUM-2; MUM-3; neo-PAP; Myosinclass I; NFYC; OGT; OS-9; pml-RARalpha fusion protein; PRDX5; PTPRK;K-ras; N-ras; RBAF600; SIRT2; SNRPD1; SYT-SSX1 or -SSX2 fusion protein;Triosephosphate Isomerase; BAGE-1; GAGE-1,2,8; GAGE-3,4,5,6,7; GnTVf;HERV-K-MEL; KK-LC-1; KM-HN-1; LACE-1; MAGE-A1; MAGE-A2; MAGE-A3;MAGE-A4; MAGE-A6; MAGE-A9; MAGE-A10; MAGE-A12; MAGE-C2; mucin k; NA-88;NY-ESO-1/LAGE-2; SAGE; Sp17; SSX-2; SSX-4; TRAG-3; TRP2INT2g; CEA;gp100/Pmel17; Kallikrein 4; mammaglobin-A; Melan-A/MART-1; NY-BR-1; OA1;PSA; RAB38/NY-MEL-1; TRP-1/gp75; TRP-2; tyrosinase; adipophilin; AIM-2;BING-4; CPSF; cyclin D1; Ep-CAM; EphA3; FGF5; G250/MN/CAIX; HER-2/neu;IL13Ralpha2; Intestinal carboxyl esterase; alpha-foetoprotein; M-CSF;mdm-2; MMP-2; MUC1; p53; PBF; PRAME; PSMA; RAGE-1; RNF43; RU2AS;secernin 1; SOX10; STEAP1; survivin; Telomerase; WT1; FLT3-ITD; BCLX(L);DKK1; ENAH(hMena); MCSP; RGS5; Gastrin-17; Human Chorionic Gonadotropin,EGFRvIII, HER2, HER2/neu, P501, Guanylyl Cyclase C, PAP.
 15. Therapeuticanti-tumour vaccine, comprising an effective amount of a compositionaccording to claim
 1. 16. Use of a composition according to claim 1, forthe manufacture of a therapeutic anti-tumour vaccine.
 17. Compositionaccording to claim 1, for use as a therapeutic anti-tumour vaccine. 18.Method for inducing, in a patient, a cytotoxic cellular response againsttumour cells or a tumour, comprising the administration to this patientof an effective amount of a composition according to claim
 1. 19. Ananticancer treatment method for inducing, in a patient, a cytotoxiccellular immune response against tumour cells or a tumour, comprisingthe administration to this patient of an effective amount of ananti-tumour vaccine according to claim 15.